Re: [PATCH i-g-t 10/16] i915/gem_exec_whisper: Fork all-engine tests one-per-engine

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 22/05/2019 11:59, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-05-16 09:57:08)
> > On 15/05/2019 20:35, Chris Wilson wrote:
> > > Quoting Tvrtko Ursulin (2019-05-14 13:57:26)
> > > > On 08/05/2019 11:09, Chris Wilson wrote:
> > > > > Add a new mode for some more stress, submit the all-engines tests
> > > > > simultaneously, a stream per engine.
> > > > >
> > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > > > ---
> > > > >     tests/i915/gem_exec_whisper.c | 27 ++++++++++++++++++++++-----
> > > > >     1 file changed, 22 insertions(+), 5 deletions(-)
> > > > >
> > > > > diff --git a/tests/i915/gem_exec_whisper.c b/tests/i915/gem_exec_whisper.c
> > > > > index d3e0b0ba2..d5afc8119 100644
> > > > > --- a/tests/i915/gem_exec_whisper.c
> > > > > +++ b/tests/i915/gem_exec_whisper.c
> > > > > @@ -88,6 +88,7 @@ static void verify_reloc(int fd, uint32_t handle,
> > > > >     #define SYNC 0x40
> > > > >     #define PRIORITY 0x80
> > > > >     #define QUEUES 0x100
> > > > > +#define ALL 0x200
> > > > >     
> > > > >     struct hang {
> > > > >         struct drm_i915_gem_exec_object2 obj;
> > > > > @@ -199,6 +200,7 @@ static void whisper(int fd, unsigned engine, unsigned flags)
> > > > >         uint64_t old_offset;
> > > > >         int i, n, loc;
> > > > >         int debugfs;
> > > > > +     int nchild;
> > > > >     
> > > > >         if (flags & PRIORITY) {
> > > > >                 igt_require(gem_scheduler_enabled(fd));
> > > > > @@ -215,6 +217,7 @@ static void whisper(int fd, unsigned engine, unsigned flags)
> > > > >                                 engines[nengine++] = engine;
> > > > >                 }
> > > > >         } else {
> > > > > +             igt_assert(!(flags & ALL));
> > > > >                 igt_require(gem_has_ring(fd, engine));
> > > > >                 igt_require(gem_can_store_dword(fd, engine));
> > > > >                 engines[nengine++] = engine;
> > > > > @@ -233,11 +236,22 @@ static void whisper(int fd, unsigned engine, unsigned flags)
> > > > >         if (flags & HANG)
> > > > >                 init_hang(&hang);
> > > > >     
> > > > > +     nchild = 1;
> > > > > +     if (flags & FORKED)
> > > > > +             nchild *= sysconf(_SC_NPROCESSORS_ONLN);
> > > > > +     if (flags & ALL)
> > > > > +             nchild *= nengine;
> > > > > +
> > > > >         intel_detect_and_clear_missed_interrupts(fd);
> > > > >         gpu_power_read(&power, &sample[0]);
> > > > > -     igt_fork(child, flags & FORKED ? sysconf(_SC_NPROCESSORS_ONLN) : 1)  {
> > > > > +     igt_fork(child, nchild) {
> > > > >                 unsigned int pass;
> > > > >     
> > > > > +             if (flags & ALL) {
> > > > > +                     engines[0] = engines[child % nengine];
> > > >
> > > > Relying on PIDs being sequential feels fragile but suggesting pipes or
> > > > shared memory would be overkill. How about another loop:
> > >
> > > Where are you getting pid_t from? child is an integer [0, nchild).
> >
> > Add a core helper to get it?
> >
> > I am coming from an angle that I remember some time in the past there
> > was a security thing which randomized pid allocation. TBH I am not sure
> > if that still exists, but if it does then it would not be good for this
> > test. May be moot point to think such security hardening measures would
> > be active on a machine running IGT tests.. hm.. not sure. But it is
> > still a quite hidden assumption.
>
> But we are not using pid_t here. It is just an array of child processes,
> with each child getting its own engine, using the child index as an
> index.

Oh right.. both is the same. Sorry, context-switching fail on my part..

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

Regards,

Tvrtko
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